Burglar-alarm.



W. T. ANDERSON, JR. BURGLAR ALARM.

APPLICATION FILED APR. 29.1908.

918,413 Patented Apr. 13, 1909.

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imrrnn STATES PATENT OFFICF' WILLinM 'r. ANDERSON, JR., F TARENTUM, PENNSYLVANIA.

BU'RGLAR- ALABM.

no. e1s,41s.

, .of the bolts 8 is arm ed on each side of the Be it known .thatl, WTLIJIAM T. Alanna To all whom it SON, Jr.', a citizen.- of the-United States of America, residing at Tarentum, in the county o'f'Alleg'heny and State of Pennsyl vania, have invented newand useful Improvements in Burglar-Alarms, of which the I following a spec1ficationI-.-

My invention. relates to burglar alarms, and 1ts primary object is the revision of a simple, durable and efficient evice of this character, which is especially. designedfor application to a stairs,v and which can be readily and quickly appliedzby an unskilled i person.

A further object tr my invention is the provision of a burglar alarm which. can-be manufactured and sold at a comparatively low cost. With the above and other objects in View, the invention consists in the; construction, combination and arrangement ofparts hereinaftcr fully described, claime(l -and illustrated in the accompanyingdrawingflvherein:

Figure 1 is a View in side elevation illus-- trating the ap lication of m. improved burglar alarm. ig. 2 is a deta' 'lan view of the tread plate. of the contact strip, and Fig. its a sectional view illustrating the manner iii-which the supporting springs are secured to the tread p ate.

Referring to the drawing by reference numerals, 1 designates the tread, and 3 the 1 riser of a stairs.

and the elements 5 is such that the plate is pivotally mounted at its inner edge above the tread of the stairs. The outer or free end of the tread plate 4 is supported by means of expansible coiled springs? which are arranged on opposite sides of the transverse center of the plate. The springs 7 are secured in applied position by means of bolts 8 which are threaded into the tread plate and which are provided with o enin s 9 for the reception of the up ver en s of t e springs, as ful y I illustrated in *ig. 4 of the drawmg. A pair 7 Specification 'of Lettera Patent.

Application flied April 29,

Fig. 3 is a detal top. plan View Patented April 13, 1909. 1903. Serial ms. 420,901.

transverse center of t e tread plate and the bolts of each are relatively spaced. The free end of t e tread plate 4 is provided on its underside with contacts 10, which are preferably constructed of latinum. The contacts 10 are adapted w en the tread plate is de ressed to engage contacts 11 on a contact strip 12 which is secured to the tread 20f the stairs. The plate- 12 is' provided with perforations-v 13 forjfthe passage of faste elements and with a binding post 15' t0 ,whic the wire 1610i anselectric circuit is secured. The. wire 'I'Z'of thecircuit is securedt'o the tread platef Aswitch 18 and a bell 19 are pivoted on of the tread plate is supported v above the tread ,2 of the stairs by means of fulcrumblocks 21iwhich are screwed into the underside ofethej plate. The outer or free endof the tread" late is curved downwardly, as at 22, over tiie outer edge of the tread. The curvedportion of the tread plate prevents the edge of the plate from being contacted with by the feet of a person ascending the stairs- In praetice, three of the burglar alarms are used, and are refer-ably secured to the first three treads- 0 the stairs. The wires17,16 and battery 20 are concealed and the bell and switch areilocated at a convenient oint.v The switch, 18 enables the device to thrown into and out of use. .When a p on ate thetread plates the free end thereo .is moved downwardly under the tension of the spring 7, resulting in the closing.

of the cir'cuit andtlie sounding of the bell. When the person steps off of the tread plate the sprin '7 returns the free end, thereof to itsnorrna position, resulting in the breaking of the circuit. The tension of the springs can be regulated by moving each spring from one of each pair of bolts to the other.

The tread plate is preferabl as large as the surface of the trend 2 an it does not in any way hinder the laying of or mar the ap earance of the stair carpet.

rom the foregoing description taken in connection with the accompanying drawing, the construction and mode of operation of the invention should be understood without a further extended description.

Chan es in the form, proportions and minor etails of construction may be made I secured to the tread, a contact secured to i the strip, and a contact secured to the tread within the scope of the claims without departing from the spirit or sacrificing any of the advantages of the invention. 1 plate.

Having fully described and illustrated .my 3. A burglar alarm including a pivotally invention, what I claim is: fmounted tread plate, a fulcrum block 1. The combination with the tread and adapted to support the pivoted end of the riser of a stairs, of a tread plate pivotally I tread plate, secured to the riser and extending over the 5 free end of tread of the stairs, a fulcrum block secured another contact secured to the tread plate. to the tread plate to support its pivoted 4. A burglar alarm com rising a ivotend, a spring secured to the tread plate to ally mounted tread plate, alhlcrum a apted support its free end, a contact strip secured 1 to support the pivoted end of the tread to the tread, a contact secured to the strip, plate, a bolt. removably secured'to the tread and a contact secured to the tread plate. plate, a spring secured to the bolt and 2. The combination with the tread and adapted to support the free end of the tread riser of a stairs, of a tread plate pivotally plate, a contact strip, a contact secured to secured to the riser and extending over the f the strip, and a contact secured to the tread tread, the free end of the plate being curved gplate. downwardly over the outer edge of the In testimony whereof I aflix my signature tread, a fulcrum block secured to the tread :inpresence of two Witnesses. plate to support its pivoted end, a bolt; WILLIAM T. ANDERSON, JUNIOR.

removably secured to the tread plate, a! Witnesses: spring secured to the bolt to support the free i CARL FRIEDRICH, end of the tread plate, a contact strip, C. E. KING.

a spring adapted to support the the tread plate, a contact, and 

